Bacterial growth occurs in many systems in which aqueous media such as water, aqueous solutions and aqueous dispersions are employed.
For example, significant biofouling can occur in many areas of photoprocessing systems and, in particular, where low flow rate washes and water recycling is used. The problem may be overcome by adding biocides to the wash water tanks when bacterial biofilm formation becomes evident visually. However at this point the biocides are not particularly effective because the bacteria have attached to surfaces to form biofilms which have built up in layers. Hence, any biocide in solution can only reach the outer biofilm layer and not the inner layers of the biofilm. Furthermore, widespread use of such biocides is not desirable because they are relatively expensive and toxic chemicals which require specialised disposal to protect the environment.
Alternative methods of inhibiting bacterial growth in aqueous media involve the gradual release of a biocide through interaction with water e.g. by leaching.
GB-A-2 223 662 describes a coating composition for seeds which comprises an organic biocide chemically bound to a polymer by a hydrolytically unstable bond. The polymer gradually hydrolyses giving controlled release of the organic biocide.